The invention relates to an electronic flat key in accordance with the features of the preamble of Claim 1.
Flat keys of this type are for example known from DE 39 02 537 C2. They are essentially composed of a grip element and a key bit, the grip element including a casing and the key bit being arranged on the casing of the grip element in a manner enabling it to be swiveled from a retracted position, in which it is located in a lateral well in the grip element casing, into an extended position. In the case of the conventional flat key the grip element casing consists of two shell-type plastics side elements joined together, which enclose an electronic switching device for remote operation of a lock or locking system. In addition, there is disposed in the grip element casing a holder which houses the batteries for supplying power to the electronic switching device. The holder is contiguous with the surface of one of the two shell-type side elements and is sealed towards the exterior by a sliding cover.
The drawbacks of these known flat keys include the fact that the side elements cannot be made of metal, for a corresponding grip element casing would mean that the transmitting or receiving elements located in the grip element casing would be electrically shadowed in an undesirable manner. However, for reasons concerned with stability and with adapting the design of the flat key to the respective vehicle, flat keys having a grip element casing made of metal are often desired.
The known keys also have the drawback that the battery compartment is relatively easily accessible and therefore time and again the sliding cover inadvertently becomes displaced and the batteries can then fall out of the battery compartment.
It is the underlying object of the invention to provide an electronic flat key on which the grip element casing consists of metal side elements constructed in the form of shells, without this essentially affecting (electrically shadowing) the transmitting and/or receiving elements located in the casing for remote operation of a lock or locking system.
In accordance with the invention this object is achieved by the features contained in Claim 1. The subsidiary claims disclose additional, particularly advantageous embodiments of the invention.
The invention is essentially based on the concept of arranging between the two metal shell-type side elements of the grip element casing a central element, in the form of a frame, made of a material that does not conduct electricity, which extends peripherally at least in sub-portions of the grip element casing as far as the outer surface of the casing and is sufficient to convey an adequate signal between the transmitting and/or receiving elements located in the grip element casing and those located in the lock zone or locking system zone.
The frame-type central element may for example be made of plastic or even rubber, and is preferably constructed in such a way that it also acts as a sealing element for sealing off the internal compartment of the grip element casing against external influences.
To prevent the battery cover from being removed unintentionally, another form of embodiment of the invention provides for the battery compartment holder situated in the grip element casing to be internally contiguous with the well for receiving the key bit, with the result that the batteries can only be inserted into the holder or removed therefrom when the key bit is in the extended position.
For rapid installation of the batteries it has proved advantageous if the batteries are placed in a separate battery compartment before being inserted into the battery compartment holder, and then the battery compartment, loaded with a plurality of batteries if appropriate, is pushed into the holder and joined to the latter via, for example, a clip-type connection.
To allow the assembly or disassembly of the flat key according to the invention to be undertaken in a straightforward manner, it has also proved expedient if at least one side element incorporates projections in predetermined peripheral zones, which projections protrude beyond the central element and by means of which said side element can be clipped onto the respective other side element.